Inverter input voltage and battery design


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JonCombat

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Jan 11, 2022
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I have a few questions about building a battery and inverter selection. What inverter / battery voltages are typically used? I would like to build a powerwall for my home. What are typical inverter input voltage ranges? 12 18650 batteries will give you a voltage range be 43-49.2V. can you oversize the system lightly to increase the voltage of the battery pack by 3.6-4.1V?
 

Oberfail

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Jun 22, 2021
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12v / 24v / 48v are common
Most people, that have big loads, use 48v to keep the losses lower. Most 48v inverters accept 40-65v, but look at the datasheet of an inverter first before you buy one.

For NMC / LCO 18650's, 14s is commonly used, 13s rarely aswell. For LFP / LiFePo4 batteries, 16s is commonly used.
 

floydR

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Aug 23, 2017
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Go 14s less stress on the battery many 48v inverters still are based on lead acid which can be near 60v down to 42v 14s gets you to 57.4v- 50.4v. The Less work the inverter has to do. 3.6v-4.1v
Later floyd
 

OffGridInTheCity

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Agree with above. Go 14s for lithium-ion (18650) and 16s for LifePo4. Will match 48v equipment perfectly and give you a wide range of choices at good prices. You could go 24v (7s lithium-ion and 8s LifePo4) but as stated above, if this is for a home powerwall - go 48v :)

If this if for 12v, the go 4s LifePo4. Neither 3s or 4s won't work for lithium-ion - the voltage ranges are just not compatible.
 
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JonCombat

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Jan 11, 2022
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I have access to Li-ion batteries. Can anyone recommend an inverter manufacturer?
 

Oberfail

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Victron / SMA - very high quality, but propriotary and expensive
Growatt, MPP Solar, Voltronic - okay-ish quality
 

Korishan

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I agree with the above the statements. Go 14s for a home powerwall application. You'll save yourself a lot of money down the road, as well as hassle. The inverters aren't much different in cost between 24 and 48V, but the "wiring" to run 24V will be at least twice what 48V would require.
If the runs are only a few feet, no big deal. But if you have the battery bank stored in one location, and the inverter in a different location (for example, on different sides of a wall with the battery 'outside' in a protected building), then the cost of wire goes up quick.

As far as brand of inverters, as Oberfail mentions, those are good qualities. The Growatt seems to be the new kid on the block, but is proving itself. On youtube, check out DavidPoz, as he's been doing tests using the Growatt inverters. I think he's even connected 3 of them in parallel for load sharing, if I remember correctly.
 

JonCombat

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I will check it out. I am located in the U.S.A. (Connecticut) it would be nice to have a local supplier for warranty/replacement parts close by.
 

JonCombat

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Go 14s less stress on the battery many 48v inverters still are based on lead acid which can be near 60v down to 42v 14s gets you to 57.4v- 50.4v. The Less work the inverter has to do. 3.6v-4.1v
Later floyd
I am looking into a BMS. I checked out Batrium. Has anyone used a Raspberry PI to monitor the BMS? They are small, cheap and have HDMI outputs for a monitor. Batrium is windows based.
 

Oberfail

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OffGridInTheCity

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Agree that Batrium is insanely expensive but it's worked well for me and I'm into year 3. The core/software/support could all be better but overall it tips to being a solid choice for large powerwalls in my judgment.

In particular it makes it easy to expand - which turned out to be the #1 key thing for me. I'm in year 3 and still processing cells / building packs and still able to buy compatible longmons for expansion. I may continue to expand for a couple of more years and have every expectation that I'll be able to. So long term existence of this product has been the #2 key thing for me.

I extract data by parsing the data file you can dump every 5 mins which is adequate for me - but others connect to it via DIY software for 'real time' info extraction.

It's also a ThingSpeak client but for ease of setup you have to use a cloud based ThingSpeak server and for me I don't put anything in the cloud. You can install a local ThingSpeak server but it looked complicated!
 

cak

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Mar 14, 2021
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I am looking into a BMS. I checked out Batrium. Has anyone used a Raspberry PI to monitor the BMS? They are small, cheap and have HDMI outputs for a monitor. Batrium is windows based.
I have heard good things about Batrium in general but the price was to much for me and I prefer DIY so the DIY BMS is what I went with. Assembly and expertise required but new skills to learn plus a great community of support. Also based on an ESP32 with direct hosted web portal to monitor and manage. Folks have also built integration with Home Assistant and other monitoring platforms. Biggest problem right now is chip shortages but every so often a group of folks get together on a group buy to scavenge everything together. https://community.openenergymonitor.org/t/diybms-v4/11292
 

gpn

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Jan 21, 2018
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I will check it out. I am located in the U.S.A. (Connecticut) it would be nice to have a local supplier for warranty/replacement parts close by.
You can buy victron stuff in the states from Northern Arizona wind and Sun or Pkys. Both ship quickly and have fair pricing. Victron carries a 5-year warranty which is neat. Of course I haven't had any of my victron stuff fail over the last 2-years I've been using it.
 
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